Recent years have seen a growing demand for path protection mechanisms for use in carrier networks operated by telecommunication service providers and the like. To offer more reliable, enhanced services in Ethernet™ transport networks, protection switching techniques are applied to logical paths carrying Ethernet frames. In this technical field, the International Telecommunication Union Telecommunication Standardization Sector provides the ITU-T G.8031 standard for Ethernet Protection Switching.
The path protection mechanism employs working and protection transport entities, or two logical paths with different routes on the network, to provide a redundant connection, unlike the link aggregation which combines physical paths between physical ports of two network devices. In normal situations, Ethernet frames and other traffic are exchanged over working entity. When the working entity fails, the traffic is switched to protection entity to maintain the ongoing communication over the network. For example, the following literature provides conventional path protection techniques:                Japanese Laid-open Patent Publication No. 2007-116275        Japanese Laid-open Patent Publication No. 2007-181010        
A single protection domain may accommodate a plurality of protected logical paths to transport a large number of user data flows. In the event of failure, the above-noted conventional techniques execute a path switching operation on an individual flow basis. Accordingly, the more user data flows are accommodated, the more time it will take to complete path switching.
In the Ethernet protection switching, the path table entry for a specific user data flow has a Virtual LAN identifier (VLAN ID) validity flag, first path enable flag, and second path enable flag, whose values may be modified to switch the path for that flow. The network device executes path protection switching of each flow with its internal software module. When there are many flows, it will take a long time until the device can finish the switching of all those flows.
Suppose, for example, that two thousand user data flows are running over the same path protection domain. In the case of failure, those flows have to be switched one by one. For example, each single flow consumes 50 μs for switching, while given system requirements dictate a maximum switchover time of 50 ms. The total switchover time for two thousand user data flows amounts to 100 ms, meaning that the network fails to meet the maximum switchover time of 50 ms.